I can’t find wakeonlan or wol packages for 15.3. Are there any alternatives available? Thanks.
wol-0.7.1-2.5.x86_64.rpm is available in the standard 15.3 repository (and should be installed by default), Maybe that’s not what you were looking for?
Alternatives for what exactly? I am not sure I understand what your goal is, but this is something that helped a few people:
https://forums.opensuse.org/showthread.php/549615-Wake-on-LAN-a-working-case
You’re right! Got confused by “There is no official package available for openSUSE Leap 15.3” in openSUSE Software and in openSUSE Software. Need to have my morning coffee **before **asking stuff in the forums 
That thread was really useful. Thanks 
Be aware that at present the search facility ( openSUSE Software ) is rather broken for 15.3 - hence the “There is no official package available for openSUSE Leap 15.3”, when in fact it does exist.
You can search all repositories that you currently have enabled by using zypper, for example:
paul@Orion-17:~> zypper se --match-exact -s wol
Loading repository data...
Reading installed packages...
S | Name | Type | Version | Arch | Repository
--+------+---------+-----------+--------+----------------------
i | wol | package | 0.7.1-2.5 | x86_64 | Main Repository (OSS)
paul@Orion-17:~>
Although that (obviously) won’t find packages from repositories you don’t have enabled.
You could also search on OBS, for example: “Search - openSUSE Build Service” but ensure if you install anything found that way it is compatible with 15.3.